Today, television receivers allow selection of external baseband audio and video signals from audio and video sources such as VCR's and videodisc players, as well as selection of broadcast television programs tuned and demodulated by a built-in tuner and intermediate frequency (IF) circuitry.
The external audio and video signals are coupled to individual input terminals (or jacks). These input terminals, and the output terminals of the internal tuner/IF circuitry, are coupled to the signal processing circuits of the television receiver via a signal switch assembly. One television receiver having multiple electronically selectable auxiliary baseband signal inputs is known from the RCA CTC-140 manufactured by Thomson Consumer Electronics, Inc., Indianapolis, Ind. This television receiver employs digital switching logic to automatically provide proper audio and video when each of the video source selections is made (i.e., tuner, AUX1 or AUX2).
U.S. Pat. No. 4,821,122 (Teskey) issued in 11 Apr. 1989 discloses a system in which in response to the reception of a “VCR ON” remote control command, a television receiver, to which the VCR is connected, automatically selects the AUX1 baseband video input as the signal source. If no signal is found at the AUX1 input, then the television receiver switches to the tuner, and tunes channel 3, and then channel 4 in succession, searching for input signals from the VCR. Thus, a user may select the VCR for viewing without knowing how the VCR was actually connected to the television receiver. However, suppose that a user has a baseband video signal source, other than the desired VCR, connected to AUX1. In this case, the automatic signal seeking function will not locate the VCR but will find an active signal at the AUX1 input, and thus will be “fooled” into selecting the signal at the AUX1 input.
U.S. Pat. No. 4,996,597 (Duffield) issued in 26 Feb. 1991 discloses a switching system which allows a user to specify which of several input connectors or channels is assigned to which of several signal sources, and store the connector or channel assignment data in memory. Thereafter, upon selection of a particular signal source, the system automatically selects the input connector or channel associated with the selected signal source in response to the stored data. The disclosed system also provides ease of use in that the television receiver automatically selects the proper input configuration when a signal source device is selected.
The emergence of high definition television (HDTV) will make available television programming services in a digital format using compressed digital video bitstreams. However, the complete transition to digital programming may take years or even decades. Thus multi-video service providers (MVSP) may likewise offer a combination of NTSC analog video programs and ATSC digital video programs. MVSPs may offer service to customers in multiple ways. First, to service customers with legacy analog television sets, a cable set-top box may include a digital MPEG decoder to convert digital signals to analog signals. In this case the consumer sees no difference in the way the system operates. Another implementation would be to provide a set-top box that offers the digital signals through a digital data bus and the analog programs through the traditional analog ports. This implementation lets the consumer take advantage of displaying the full resolution of the picture if they have a digital television.
‘Dual-mode’ systems have unique requirements in that a consumer may wish to switch between channels requiring a switch of the physical input ports on a television set or converter box. For a ‘dual-mode’ system to function properly, it is necessary for a television set to be knowledgeable about the particular configuration of the video source, display, and auxiliary devices.
In addition to the multiple signals produced by a single device such as a “dual mode” device, complex systems producing many signals may be created by interconnecting electronic devices such as television receivers, display devices, video-cassette recorders (VCR), digital versatile disk (DVD), direct broadcast satellite (DBS) receivers, and home control devices (e.g., a security system or a temperature control device) The interconnection may be done using a data bus such as the Consumer Electronics Bus (CE Bus), and the IEEE 1394 High Performance Serial Bus.
A bus protocol typically provides for communicating both control information and data. For example, CEBus control information is communicated on a “control channel” having a protocol defined in Electronics Industries Association (EIA) specification IS-60. On an IEEE 1394 serial bus, control information is generally passed using the serial bus' asynchronous services. Control information for a particular application can be defined using for example, CAL (Common Application Language) or AV/C.
Televisions and display devices typically have one or more inputs for gathering source signals for display. For example, a typical television may have an antennae input for tuning the broadcast RF television signals plus one or more auxiliary inputs for providing a higher quality base-band video and audio signal for display. One may use the antennae input for signals coming from a cable decoder box and use one set of auxiliary inputs for attaching a DVD or VCR player. Depending on the specific television product, multiple sets of auxiliary inputs may be available.